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Year : 2022 | Volume
: 14
| Issue : 2 | Page : 114-120
Troubleshooting ocular prosthesis: A case series
Sivaranjani Gali, V Midhula, Anita Naimpally, Hima B Lanka, Keerthy Meleppura, Chinmaya Bhandary
Department of Prosthodontics, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bangalore, Karnataka, India
Correspondence Address:
Dr. Sivaranjani Gali
Department of Prosthodontics, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bangalore, Karnataka
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jpbs.jpbs_750_21
Abstract
This case series reports on clinical challenges faced during the rehabilitation of custom ocular prosthesis. Each of these cases relate the challenges of making ocular impressions for an improved retention and support of ocular prosthesis and presents the significance of scleral contouring in overcoming cosmetic defects of the eye. In addition, evaluation of scleral wax pattern, methods of iris location and scleral characterization methods in ocular rehabilitation are further discussed.
Keywords: Ocular impressions, ocular prosthesis, scleral characterization, scleral wax pattern
Introduction 
Ocular prostheses significantly enhance psychological and physical well-being of patients suffering from pathological disfigurements of the eyes.[1]
Ocular prostheses are generally available as stock eye prostheses in various sizes or can be made as a custom prosthesis. A stock eye prosthesis, as they are readily available, takes less time but has limitations of lack of adaptation to the ocular tissue bed. This limitation results in hollow spaces between the prosthesis and ocular tissue bed, resulting in mucous collection and infection.[2] Custom prosthesis has the advantage of adapting closely to the patient's tissues and can better mimic the patient's sclera and iris position.[3] The restoration requires the prosthodontist to be aware of the ocular anatomy while recording ocular impressions to precisely locate iris position and to manage the cosmetic defects such as ptosis and reduced palpebral fissure of the defective eye. A case series of rehabilitation with custom ocular prosthesis with clinical challenges is presented. The procedural steps of ocular impressions, iris-scleral wax trial, scleral characterization and processing of the ocular prosthesis were followed in all of the case reports and shown as a flowchart in the [Figure 1].
Figure 1: Flowchart of procedural steps in the fabrication of a custom ocular prosthesis Case Report 1 A 40-year-old male, presented to the department of prosthodontics, with Class III phthisis bulbi, discolored sclera, corneal opacity, ptosis, healed ocular bed and narrow palpebral fissure in [Figure 2]. History revealed injury to the left eye followed by ophthalmic surgery about 16 years back. The patient chiefly complained of mucous discharge and has since been wearing stock eye prosthesis. Clinical examination revealed healed tissue bed and unesthetic white sclera of the stock eye prosthesis with disoriented iris. Phthisis bulbi, a degenerative condition of the eye, occurs as an inflammatory healing response to trauma, surgery, malignancies and systemic diseases.[4] Ocular rehabilitation of phthisis bulbi have been in the form of stock or custom eye prosthesis.[5] Pre- and postoperative photographs are presented in [Figure 2]. The case requires restoration of the ptosis with the demanding esthetics of the sclera in shade and color and iris position.
Case Report 2 A 23-year-old male patient presented with a chief complaint of facial disfigurement due to defect in the right eye. His history revealed trauma in childhood with enucleation of the ocular contents of the right eye. Reconstruction of the orbital socket was done with adipose tissue graft. Ocular conformer was placed post graft surgery, a week after to prevent the collapse of the tissue graft. The patient presented with ptosis, and healed eye socket. Pre- and postoperative photographs are presented in [Figure 3].
Case Report 3 A 63-year-old male patient complaining of dissatisfaction of a stock ocular prosthesis with respect to its colour, size, and comfort wanted a new ocular prosthesis. Patient had a history of trauma and evisceration of the ocular content of the right eye with ptosis. Pre- and postoperative photographs are presented in [Figure 4].
The mentioned case reports 1, 2 and 3 will be abbreviated as CR1, CR2 and CR3, respectively, throughout the paper.
Discussion Clinical challenges in making ocular impressions in the correction of ptosis, scleral wax patterns and locating iris position are discussed. Informed consent was taken from patients, and patients were explained about the procedures.
Ocular impressions and correction of ptosis
The topography of the affected eye is recorded with dental materials such as impression waxes, ophthalmic alginate, tissue conditioners and elastomeric impression materials.[6–10] Low viscosity alginate, modified impression technique, medium viscosity and ophthalmic alginate with autoclaved titanium stock trays were used to record the impression surfaces accurately.[11],[12],[13],[14],[15],[16]
A thin layer of 2% lignocaine topical gel has to be applied to the ocular tissues to avoid irritability.[12] Fixed gaze of the patient in the upright seated position aids in accurate ocular impression recording. The tarsal plates with eyelid margins need to be recorded to support the drooping eyelid. The margins must be sculpted in such a way that the prosthesis fabricated from this impression must support the drooping eyelid without over-contouring the inferior margin. A near-perfect impression can be made with prudent impression-taking and functional movements of the eye by the patient.[11] Enough extension into the inferior palpebral fissure must be present for adequate retention of the tray.
The ocular tray must be checked for adequate margins and overextensions must be trimmed. The tray could be a stock tray (conformer), stock trays modified, wax scleral blank, an existing ocular prosthesis or a customized tray made from the existing ocular shell. The ocular stock trays are available in different sizes according to the anatomical contour of the ocular tissues such as long oval, rounded with trochlear cut, triangular for deep, pointed superior fornix, mixed shape with posterior horn for special support.[2]
Allen and Webster[17] proposed a modification of the stock ocular tray with a hollow stem and perforations using ophthalmic alginate to record the tissue surfaces.[18] Miller used clear acrylic custom ocular trays with hollow stem and perforations.[19] Stock ocular prosthesis can also be modified as ocular trays, but this technique is limited by the availability of stock eye prosthesis.[16],[18],[20] Ow and Amrith described the use of tissue conditioner material for modification of the stock ocular prosthesis.[11]
Perforated, clear, auto-polymerized acrylic tray were made from existing ocular prosthesis in CR1 and conformers in CR2 and CR3. Wide hole perforations were made to hold the impression materials, and a 1-cm diameter hole was placed in the centre of the tray to help dispense the impression materials in the eye socket. In CR1, secondary impression was made with medium body polyvinyl siloxane impression material [Figure 5]. In CR2 and CR3, monophase polyvinyl siloxane impression material was used [Figure 5]. The patient was made to sit in an upright position and perform functional movements of upward, downward, medial, and lateral movements of the eye. It is important for the prosthodontist to be aware of the landmarks to be recorded and to be able to read the ocular impressions. The landmarks of ocular impressions are presented as nasal canthus, temporal canthus, the tarsal plates, and presence of conjunctival folds, as shown in [Figure 6] in CR1. A proper ocular impression must record the required landmarks.
Figure 5: Custom impression ocular tray made from existing stock ocular prosthesis of CR1 in (a1), with impression tip in (a2); of CR2, made from conformers using heavy body siloxane in (b1) and clear acrylic tray with central hole and perforations in (b2); of CR3, made from conformer in (c1), clear acrylic tray in (c2) and monophase impression in (c3)
Figure 6: Reading an ocular impression: (a) Tarsal plates of upper eyelid, (b) Palpebral folds, (c) Scleral folds, (d) Medial canthus, (e) Lateral canthus, (f) Conjunctival foldsIn all the case reports of CR1, CR2 and CR3, patients presented with ptosis. Ptosis, also known as blepharoptosis refers to a drooping eye lid with narrowing of the palpebral fissure.[21],[22] Pseudo-ptosis results from a lack of orbital volume, from microphthalmus, enophthalmos, phthisis bulbi, or poorly fitted prostheses.[23] It is managed conservatively by augmenting the superior portion of the ocular prosthesis.[24] If the weight of the prosthesis is increased beyond the critical value, it causes downward displacement or distortion of the lower lid.[24] The ocular trays must therefore support the tarsal plates and the material must sufficiently displace the tissues to fill the supraorbital fold. A tongue-like thin material in the fornix suggests a deep space to be filled by the impression material in the supraorbital fold and more wax to be added at the superior aspect of the corneo-scleral junction. It is critical for the impression extend to the fornix, in the lower eyelid, for sufficient retention of the prosthesis. Adding wax to the scleral pattern must thrust the upper tarsus of the eyelid more forward and upward to overcome ptosis and widen the palpebral fissure for sufficient eye opening, accommodated with a shelf over the corneo-scleral junction to support the eyelids and a bulge superiorly to fill the eyelids.[11]
Practical difficulties encountered during impression-making
Ocular impressions may not be able to record the shape and form of the eye socket with an unsupported impression material, as surrounding tissues around the socket could easily displace the impression material. Hence, a supporting form for impression materials such as ocular trays are required. In contrast, ocular impressions were made with high viscosity elastomers without the use of ocular trays to prevent the possibility of distortion caused by ocular trays during impression-making.[3]
Some of the difficulties during ocular impressions are sensitivity and intolerance of mucosa of ocular tissues to impression materials when in contact with them for a prolonged period. As a result, patients often experience discomfort and irritation. Ocular impression materials must therefore not cause irritation to the soft tissue. Impression techniques must facilitate short contact time, be simple to perform and ensure accurate adaption to mucosal surface of the eye socket.[10] Conventional impression materials such as dental waxes, dental compound, irreversible hydrocolloids and elastomers were used as ocular impression materials. Typical dental alginate containing flavors and colorants can cause inflammation of the eye sockets. Due to their poor adherence to acrylic ocular prosthesis and tissue intolerance, customized ophthalmic alginate, tissue conditioners and elastomeric impression materials were recommended.[9]
Verification of scleral wax pattern
The curvature of the scleral wax pattern in CR 1 was verified with Hertel's exophthalmometer, a device used to measure the curvature from the lateral orbital rim to the corneal apex in CR1. Equal measurements read on the mirror of the numerical scale on either side of the device confirmed the nature of the wax pattern to that of the healthy eye as shown in [Figure 7]. In reported case studies, the scleral wax pattern were evaluated subjectively, either against the patient face in the lateral profile or by verifying the forward position of the eyelids.[25] An exophthalmometer assesses the anterior portion of the globe, the distance from the vertex of the cornea to the lateral orbital margin. It consists of a sighting device (mirror) placed lateral to the ruler to observe the calibrations (measurement), thus restoring the affected globe position similar to the normal globe position. The device is used to identify enopthalomos, fractures and neoplasms of the eye and orbital disorders.[26] Hertel's exophthalmometer helps to verify the curvature of the sclera wax pattern, more objectively in the present technique, as shown in [Figure 3].[26]
Figure 7: Hertel's exophthalmometer used to verify sclera wax pattern curvatureIris location
Bilateral symmetry is crucial in iris positioning, which is similar to the significance of interpupillary line and horizontal reference planes in tooth rehabilitation. For extraoral maxillofacial prosthesis, the horizontal plane is captured by positioning the patient in natural head position (NHP), also called esthetic reference position.[9] NHP is the position of the head most comfortable for a patient gazing at the horizon.[8]
The positioning of the iris is an important step in the fabrication of custom-made ocular prosthesis. Centering the iris with a constant glaze in NHP is critical for esthetics and symmetry in the prosthesis.[2],[27],[28],[29] The iris of the stock eye prosthesis was selected based on the patient's contralateral eye in CR1 and CR2, while in CR3, digital photographs of the contralateral eye were used. Eyewear framework with graph grid and pupillometer were used to locate the iris position in CR1 and CR3, respectively [Figure 2] and [Figure 4]. The nose pads and temples of the eye glass used in CR1 can further help in stabilizing the graph grid. Centering of the iris was done using a pupillary distance index scale in CR2, as shown in [Figure 3]. Some of the challenges of locating the iris position were that the graph grid was difficult to adapt to pre-fabricated eyewear framework due to its curvature, and its transfer was difficult to scleral wax pattern in CR1. The card pupillometer resembling an eyewear could have been more precise with its readings, but its transfer to wax pattern in the patient was comparatively easier in CR2. The pupillary distance scale index had limitations of not being stabilized and its position on patients may vary each time in CR3.
Many authors have proposed various techniques to position the iris symmetrical to the adjacent eye in the NHP reference plane. As early as in 1969, Robert et al. used an ocular pupillometer for the alignment of the eye prosthesis.[6] A flexible transparent graph grid was used by Sinha et al. and Guttal et al.; however, the grid could lead to inaccurate transferring of the iris position.[30–32] Medio-lateral canthi of the eye were previously used to locate iris position and transfer its position with eye glass grid to the ocular stone model. Few authors such as Chamaria et al., Shetty et al. and Aurora et al. proposed methods of iris positioning with the use of facebow along with scale and graph frame. However, this method cannot be used in cases with extensive maxillofacial defects or auricular defects, and scientific evidence relating the Frankfort horizontal (FH) plane and the NHP plane are insufficient.[29],[33],[34] Gupta et al.[24] fabricated a custom-made metal frame single eye graph grid although since it is a single eye frame, its reliability of symmetry is questionable. Iris locators such as the pupillometer, Boley gauge, transparent grids and pupillary distance ruler have limitations of transferring its location on the sclera wax pattern to the ocular stone model.[35]
Scleral characterization
The challenging part of ocular prosthesis is in simulating the human ocular anatomy with prosthetic materials and creating the perfect illusion of contralateral eye.[36] Ocular prostheses in CR1, CR2 and CR3 were processed with heat polymerized medical grade acrylic resins, and characterization was done with acrylic paints with extrinsic stains and silk threads, which were incorporated for simulating the blood vessels of the eye. The ocular prosthesis in CR1, CR2 and CR3 was processed following compression molding technique with tooth colored heat cure acrylic of desired base shades. A layer of clear heat cure acrylic resin was added to the external surface ocular prosthesis and acrylized to secure the characterization. Finishing and polishing was done using various grids of silicone buffs to obtain good finish for insertion. Polishing of prosthesis is critical to reduce secretions and trauma to the mucosa of the ocular socket. Post-insertion instructions for cleaning, placement and removal of the prosthesis were given to the patients.
Practical challenges encountered during processing
It is essential that the shade of the scleral portion of acrylic prosthesis matched the scleral shade of the contralateral eye. Care has to be taken during processing of acrylic ocular prosthesis, as monomer content can cause porosity. Elimination of residual monomer while polymerization of acrylic resin is important to reduce conjunctival irritation in patients. This can be achieved through reverse curing protocol and double curing method. Monopoly syrup was used with acrylic stains to maintain original color of the prosthesis as it seals acrylic paints.[37–39] Fading of acrylic paints were reported with aging and requiring re-fabrication of the prosthesis. Ceramic stains on a scleral veneer were fabricated using IPS e-max press for esthetics. However, this technique needs additional steps, is expensive and is technique-sensitive due to the bond between the acrylic and porcelain.[40]
Conclusion A proper ocular impression must contain the required landmarks of nasal canthi, temporal canthi, the tarsal plates, and presence of conjunctival folds for an improved retention, support and esthetics of ocular prosthesis. Hertel's exophthalmometer provides an objective evaluation of scleral wax contour. An optimal method of iris location such as pupillometer that facilitates easy and precise transfer to scleral wax pattern must be selected. Care must be taken during scleral characterization to reduce porosity of acrylic ocular prosthesis and it must be well-polished to reduce accumulation of secretions in the eye socket.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s)- has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
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